diff --git a/active_admin_filters_visibility.gemspec b/active_admin_filters_visibility.gemspec
index 86ccded..44a5748 100644
--- a/active_admin_filters_visibility.gemspec
+++ b/active_admin_filters_visibility.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |s|
 
   s.required_ruby_version = '>= 3.3'
 
-  s.add_dependency 'activeadmin', '>= 3.2', '< 4.0'
+  s.add_dependency 'activeadmin', '>= 3.2', '< 4.0.0.a'
 
   # Whitelist, not a reject list: a new directory in the repo does not
   # reach consumers until it is named here. The reject form needs a new
diff --git a/spec/support/rails_template.rb b/spec/support/rails_template.rb
index 9a755f8..d760ecd 100644
--- a/spec/support/rails_template.rb
+++ b/spec/support/rails_template.rb
@@ -21,10 +21,14 @@
 inject_into_file "app/models/author.rb", "  validates_presence_of :name\n  validates_uniqueness_of :last_name\n", after: "ApplicationRecord\n"
 inject_into_file "app/models/post.rb", "   validates_presence_of :author\n", after: ":author\n"
 
-# Add ransackable_attributes for Ransack 4+
+# Add ransackable_attributes/associations for Ransack 4+ (Ransack 6 raises
+# when a model leaves ransackable_associations undefined)
 inject_into_file "app/models/author.rb",
   "  def self.ransackable_attributes(auth_object = nil)\n" \
   "    [\"name\", \"last_name\", \"birthday\", \"created_at\"]\n" \
+  "  end\n" \
+  "  def self.ransackable_associations(auth_object = nil)\n" \
+  "    []\n" \
   "  end\n",
   after: "ApplicationRecord\n"